const

     The Const keyword is used to start a section of constant definitions.

     The section is terminated by the next keyword in a program. Within the section, one or more constants may be defined. These can be a mixture of normal or typed constants or expressions.

     When passing data to a routine (function or procedure), you can prefix the parameter definition with Const if the value is never updated within the called routine. This improves performance, clarifies routine operation, and prevents accidental updates of the value.

Example

    Download This Source for Free Pascal

 Const
  MAX_LINES = 3;
  CRUDE_PI  = 22/7;
  HELLO     = 'Hello World';
  LETTERS   = ['A'..'Z', 'a'..'z'];
  DECISION  = True;

var
  i : Integer;

begin
  // Display our crude value of Pi
  Writeln('Crude Pi = ',CRUDE_PI);

  // Say hello to the WOrld
  Writeln(HELLO);

  // Display MAX_LINES of data
  for i := 1 to MAX_LINES do begin
    // Do some checking - note that Char(i+64) = 'A'
    if DECISION and (Char(i+63) in LETTERS)
    then Writeln(Char(i+63),' is a letter')
    else Writeln(Char(i+63),' is not a letter');
  end;
end.

Output

Crude Pi =  3.1428571428571429E+0000
Hello World
@ is not a letter
A is a letter
B is a letter

See Also

Function, Out, Procedure, Type, Var.

Gary Funk
BoardWatch Magazine